The goal of the proposed work is to investigate the feasibility of performing three-dimensional ultrasonic imaging form within the vascular system. The purpose for this research is to provide a means of guiding intravascular therapies: specifically, angioplasty using excimer lasers and a fiber optic delivery system. This project will focus upon development of an imaging method which can provide multi-planar images of the volume directly ahead of the laser catheter. Images of this type, obtained and displayed in real-time, will provide the surgeon with valuable guidance and assist during the course of laser angioplasty. The ultrasonic imaging techniques developed during the course of this project will form the basis for an instrument dedicated to guidance of laser angioplasty procedures.